Valve control apparatus and electric driving apparatus

ABSTRACT

A valve control apparatus is provided with a valve, a shaft supporting the valve, an end-gear of an actuator driving the valve. The shaft is press-inserted into the end-gear. A stopper disposed on the shaft regulates a valve operation range. The end-gear can engage with the middle gear of the reduction-gears mechanism even in out of the gear-operation-angle range. When a rotation angle sensor detects a rotation angle of the end-gear in out of the gear-operation-angle range, it is determined that a malfunction occurs in a rotation-force-transmitting path.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Applications No.2010-149284 filed on Jun. 30, 2010, and No. 2010-160184 filed on Jul.15, 2010, the disclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a valve control apparatus including avalve and an actuator. The valve opens/closes a fluid-passage and theactuator drives the valve. Especially, the valve control apparatus isused for opening/closing an intake passage communicating with acombustion chamber of an internal combustion engine. Further, thepresent invention relates to an electric driving apparatus which drivesa driven member by use of a driving force of an electric motor.

BACKGROUND OF THE INVENTION

Conventionally, a valve control apparatus has a valve which opens/closesan intake passage communicating with a combustion chamber of an internalcombustion engine, a shaft supporting the valve, and an actuator drivingthe valve in order to control an intake air flow rate. The actuator hasan end-gear receiving a driving force from an electric motor (drivingsource). The end-gear is connected to the shaft, so that the valve andthe actuator are connected to each other. Refer to JP-2004-124933A(GB-2393218A) and JP-2009-013934A (US-2009/0007875A1).

FIG. 6 shows a valve control apparatus 100 shown in JP-2004-124933A. Anactuator 101 is provided with an end-gear 103 which is made of resinmaterial and receives a driving force from an electric motor (drivingsource). A shaft 104 made of metallic material is press-inserted into ahole 106 of the end-gear 103, whereby the shaft 104 is connected withthe end-gear 103. A rotation of the end-gear 103 is transmitted to thevalve 107 through the shaft 104.

A housing 109 has a stopper (not shown) to which a stopper-portion (notshown) of the end-gear 103 confronts so that an operation range of thevalve 107 is regulated. That is, the stopper regulates an angularoperation range of the end-gear 103 so that the operation range of thevalve 107 is restricted. Further, the valve control apparatus 100 isprovided with a sensor (not shown) which detects a rotational angle ofthe end-gear 103, so that a position of the valve 107 is detected.

In this valve control apparatus 100, since the valve 107 is connected tothe actuator 101 by press-inserting the shaft 104 into the end-gear 103,its manufacturing cost is relatively low.

However, in this valve control apparatus 100, if a press-insertingportion between the shaft 104 and the end-gear 103 is damaged, thesensor detecting the rotational angle of the end-gear 103 can not detectthis malfunction. That is, a malfunction in a driving-force-transmittingpath can not be detected.

If the press-inserting portion is broken, it is likely that the rotationof the end-gear 103 is restricted by the stopper and only the shaft 104may spin free. In such a case, even though the end-gear 103 isrestricted by the stopper, the valve 107 rotates over a restrictedrange. Since the sensor detects only the rotational angle of theend-gear 103, it can not be detected that the valve 107 rotates over thenormal range.

In order to detect the above malfunction, it is conceivable that anothersensor directly detecting a rotational angle of the shaft 104 isnecessary. However, another sensor increases the manufacturing cost.

FIG. 7 shows a valve control apparatus 200 shown in JP-2009-013934A. Asensor 201 directly detects a rotational angle of a shaft 202 so that anopening degree of the valve 203 is detected. the shaft 202 rotates overa normal rotational range of the valve 203 due to a breakage in aconnection portion between a shaft 202 and an end-gear 204, the sensor201 outputs a detection value which indicates that the rotational angleof the shaft 202 is abnormal. Thus, it can be detected that the valve203 has a malfunction.

However, in this valve control apparatus 200, a configuration ofconnecting portion between the valve 203 and the actuator 205 becomescomplicated. Further, a gear-holding member 206 for connecting theend-gear 204 to the shaft 202 and a sensor-holding member 208 forholding a magnet 207 on the shaft 202 are necessary, which increase thenumber of parts and increase the manufacturing cost. Thus, even in thevalve control apparatus 200, a malfunction in a connecting portionbetween the shaft 202 and the end-gear 204 is not detected with lowcost.

It is well known that an electric driving apparatus drives a valve,which corresponds to a driven member, by use of a driving force of anelectric motor. The electric driving apparatus is applied to a valvecontrol apparatus for an internal combustion engine, which adjusts anintake air quantity or an exhaust gas quantity.

The electric driving apparatus is provided with a mechanism which holdsa mechanical position of the driven member. For example, in a case thatthe electric driving apparatus is applied to a tumble-control-valve(TCV) apparatus, a reduction-gears mechanism is provided with a stopperso that the driven member is mechanically held at a full-open positionor a full-close position.

In such an electric driving apparatus, when the driven member ismechanically held, the electric current supplied to the electric motoris stepwise increased. For example, when the TCV-apparatus rotates atumble-control valve toward the full-close position, the electriccurrent supplied to the electric motor varies as shown in FIG. 17. Thatis, when the electric motor is energized, the electric current istemporarily rapidly increased due to an inrush current, and then theelectric current is decreased. When the unheld driven member ismechanically held, the electric current supplied to the electric motoris stepwise increased. When the driven member is not mechanically held,the condition of the driven member is referred to as an unholdcondition, hereinafter. Also, when the driven member is mechanicallyheld, the condition of the driven member is referred to as a holdcondition, hereinafter.

It has been needed to correctly determines whether the condition of thedriven member is normally changed from the unhold condition to the holdcondition without respect to the stepwise increase in the electriccurrent.

JP-8-19172A and JP-2005-151766A show an electric circuit configurationin which it is determined that a malfunction occurs when the electriccurrent supplied to the electric motor exceeds a specified threshold.However, in this electric circuit, the change from the unhold conditionto the hold condition is not determined as a normal change.

JP-2001-4674A shows an electric circuit configuration in which thesupplied electric current is integrated so that an over-current due to ashort circuit is distinguished from a normal electric current increasedue to the condition change from the unhold condition to the holdcondition. However, in this electric circuit, it is likely determinedthat no malfunction occurs even if a malfunction other than over-currentoccurs.

SUMMARY OF THE INVENTION

The present invention is made in view of the above matters, and it is anobject of the present invention to provide a valve control apparatuswhich enables to detect a malfunction with low cost.

Also, the present invention is made in view of the above matters, and itis another object of the present invention to provide an electricdriving apparatus which is able to determine whether a driven member issurely moved from the unhold condition to the hold condition.

According to the present invention, a valve control apparatus has avalve opening/closing a fluid passage, a shaft supporting the valve andan actuator driving the valve. The shaft is press-inserted into apress-insert hole formed in an end-gear of the actuator.

Since the valve is connected to the actuator by press-inserting theshaft into the end-gear, its manufacturing cost can be made lower.

Further, the shaft has an exposed portion which is out of thepress-insert hole. A stopper radially extending from the exposed portionis provided to the shaft. A housing has a stopper surface with which thestopper is brought into contact, so that a valve operation range isregulated. Still further, the valve control apparatus has a sensordetecting a rotation angle of the actuator, and a malfunction detectingmeans for detecting a malfunction in a rotation-force-transmitting pathto the shaft.

The end-gear has gear teeth comprised of inside gear teeth and outsidegear teeth. The inside gear teeth engages with the gear of the motor ina gear-operation-angle range of the end-gear which corresponds to thevalve operation range. The outside gear teeth engage with the gear ofthe motor in out of the gear-operation-angle range. The end-gear canengage with a gear of a motor even in out of the gear-operation-anglerange.

The malfunction detecting means determines that a malfunction occurswhen the end-gear rotates over the gear-operation-angle range and thedetection value of the sensor is out of the normal detection valuescorresponding to the valve operation range.

According to the above, by detecting the rotation angle of the actuator,a malfunction in a rotation-force-transmitting path can be detected.Thus, it is unnecessary to directly detect the rotation angle of theshaft in order to find a malfunction. The manufacturing cost is notincreased. A damage of a connecting portion of the shaft and theend-gear can be detected with low cost.

According to the present invention, an electric driving apparatusincludes an electric motor generating a driving force while receiving anelectric current; an electric current detecting means for detecting theelectric current supplied to the electric motor; and a control means forcontrolling an energization to the electric motor so that the drivingforce is transmitted to a driven member in order to vary a displacementmagnitude which represents at least one of a variation in position ofthe driven member and a variation in posture of the driven member.

The displacement magnitude includes a hold value at which the drivenmember is mechanically held and the displacement magnitude does not varyeven though the driving force is continued to be transmitted from theelectric motor to the driven member so as to vary the displacementmagnitude in one direction. The electric current supplied to theelectric motor is stepwise increased when the displacement magnitudereaches the hold value after the displacement magnitude has been variedin one direction.

The control means stores a threshold regarding the electric currentsupplied to the electric motor for determining whether the displacementmagnitude normally reaches the hold value in a case that the electricmotor is controlled in such a manner that the displacement magnitudereaches the hold value after the displacement magnitude has been variedin one direction. After the electric motor is energized, the electriccurrent exceeds the threshold temporarily due to the inrush current.Then, the electric current is lowered than the threshold. After that,when the electric current excesses the threshold again, it is determinedthat the displacement magnitude normally reach the hold value.

Thereby, it can be able to determine whether the driven member isnormally moved from the unhold condition to the hold condition.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome more apparent from the following description made with referenceto the accompanying drawings, in which like parts are designated by likereference numbers and in which:

FIG. 1 is a fragmentally sectional view showing a tumble-control-valvecontrol apparatus according to a first embodiment;

FIG. 2 is an enlarged cross sectional view showing an essential portionof the tumble-control-valve control apparatus according to the firstembodiment;

FIG. 3A is a cross sectional view showing a stopper;

FIG. 3B is a plain view of an end-gear according to the firstembodiment;

FIG. 4A is a cross sectional view showing a stopper;

FIG. 4B is a plain view of an end-gear according to a second embodiment;

FIG. 5 is a cross sectional view showing a stopper according to a thirdembodiment;

FIG. 6 is a cross sectional view showing a conventional valve controlapparatus; and

FIG. 7 is a cross sectional view showing a conventional valve controlapparatus.

FIG. 8A is a cross sectional view showing an essential part of a TCVapparatus according to a fourth embodiment;

FIG. 8B is a cross sectional view showing a stopper configuration of theTCV apparatus according to the fourth embodiment;

FIG. 9A is a chart showing a circuit configuration of an electricdriving apparatus;

FIG. 9B is a graph showing an electric current supplied to the electricmotor;

FIG. 10A is a chart for explaining a lock-current in a case that bothbrushes are in contact with a single commutator;

FIG. 10B is a chart for explaining a lock-current in a case a singlebrush is in contact with two brushed;

FIG. 11 is a main flowchart for operating an electric driving apparatusaccording to the fourth embodiment;

FIG. 12 is a sub-flowchart for operating an electric driving apparatusaccording to the fourth embodiment;

FIG. 13 is another sub-flowchart for operating an electric drivingapparatus according to the fourth embodiment;

FIG. 14 is a chart showing a circuit configuration of an electricdriving apparatus according to a fifth embodiment;

FIG. 15A is a chart showing a table data according to the fifthembodiment;

FIG. 15B is a chart for explaining an update of the table data accordingto the fifth embodiment;

FIG. 16A is a graph showing an electric current supplied to the electricmotor according to a sixth embodiment;

FIG. 16B is a graph showing a relationship between a frequency ofPWM-signal and a sampling frequency; and

FIG. 17 is a graph showing an electric current for explaining aconventional driving apparatus.

DETAILED DESCRIPTION OF EMBODIMENTS First Embodiment

[Structure of first embodiment]

Referring to FIGS. 1 to 3, a first embodiment of the present inventionwill be described. In this embodiment, the present invention is appliedto a tumble-control-valve control apparatus, which is referred to as aTCV control apparatus, hereinafter. The TCV control apparatus adjustsflow passage areas of intake passages 2 each of which communicates witha combustion chamber of each cylinder of an internal combustion engine,whereby tumble flow is generated in each combustion chamber.

The TCV control apparatus is provided with an intake manifold (housing)3 defining an intake passages 2 therein, a valve 4 opening/closing theintake passage 2, a shaft 5 supporting the valve 4, an electronicactuator 6 driving the valve 4 through the shaft 5, a rotation anglesensor 7 detecting an opening degree of the valve 4, and an electroniccontrol unit (ECU: not shown) receiving detection signals from therotation angle sensor 7.

The intake manifold 3 is a casing which forms a plurality of intakepassages 2 and is made of polyamide resin. Each of intake passages 2 hasrectangular cross section and communicates with each intake port (notshown) of a cylinder head.

A tumble control valve, which is referred to as TCV hereinafter, isprovided in the intake manifold 3 in order to generate tumble flow inthe combustion chamber.

The TCV is comprised of a valve housing 11 accommodated in a housingstorage chamber 10 of the intake manifold 3 and the valve 4 which isrotatably accommodated in the valve housing 11. The number of thehousing storage chamber 10 is equal to the number of the cylinders. Eachof the valve housings 11 is held in each housing storage chamber 10.

The intake manifold 3 and the valve housing 11 respectively havepenetrating holes 13, 14 through which the shaft 5 is rotatablyinserted.

The shaft 5 supports the valve 4 and its end portion is connected to theactuator 6. The shaft 5 is made of metallic material and has polygonalcross section.

Further, the intake manifold 3 has an accommodation chamber 17 whichaccommodates a part of the actuator 6. The intake passage 2 communicateswith the accommodation chamber 17 through the penetrating holes 13, 14.

The valve 4 is made of polyamide resin. A rotation axis of the valve 4extends in a direction perpendicular to an air flow direction in theintake passage 2. The valve 4 has a polygonal hole 19 through which theshaft 5 is inserted. The valve 4 and the shaft 5 rotate together. Thecross section of the polygonal hole 19 is substantially the same as thecross section of the shaft 5, whereby a relative rotation between theshaft 5 and the valve 4 is prevented.

The valve 4 is rotated in the valve housing 11 to vary the flow passagearea of the intake passage 2. When the flow passage area of the intakepassage is reduced, the tumble flow is generated in the combustionchamber. Such a tumble flow improves a combustion efficiency and fueleconomy, and reduces emissions.

As shown in FIG. 1, the valve 4 has a notch portion 20. When the valve 4fully closes the intake passage 2, a rectangular aperture is definedbetween the valve 4 and the valve housing 11 by the notch portion 20.The intake air flows through this rectangular aperture, so that thetumble flow is generated in the combustion chamber.

When the valve 4 is fully opened in its operational range, the flowpassage area of the intake passage 2 becomes maximum.

When the valve 4 is fully closed in its operational range, the flowpassage area of the intake passage 2 becomes minimum.

It should be noted that the valve operational range represents arotational angle range within which the valve 4 can be rotated.

The rotational angle range of the valve 4 is defined by stoppers (notshown). When the valve 4 is fully closed, one of stoppers is in contactwith the valve 4. When the valve 4 is fully opened, the other stopper isin contact with the valve 4.

The actuator 6 is provided with an electric motor (not shown), areduction-gears mechanism and an actuator case 21 which accommodates thereduction-gears mechanism.

The reduction-gears mechanism includes a motor gear connected to anoutput shaft of the electric motor, a middle gear engaging with themotor gear, and an end-gear 25 engaging with the middle gear.

The end-gear 25 made of polyamide resin has an engaging portion 27 and agear portion 28. The engaging portion 27 defines a press-insert hole 26therein. The gear portion 28 is engaged with the middle gear (notshown). The engaging portion 27 extends from the gear portion 28, andhas a middle-diameter portion 31 and a small-diameter portion 32. Thediameter of the middle-diameter portion 31 is smaller than that of thegear portion 28, and the diameter of the small-diameter portion 32 issmaller than that of the middle-diameter portion 31.

The press-insert hole 26 extends along a center axis of thesmall-diameter portion 32 and the middle-diameter portion 31. An endportion 33 of the shaft 5 is press-inserted into the press-insert hole26, whereby the shaft is concentrically connected to the end-gear 25.The shaft 5 and the end-gear 25 rotate together. This end portion 33 ofthe shaft 5 is referred to as a press-insert portion 33. The crosssection of the press-insert hole 26 is substantially the same as thecross section of the shaft 5, whereby a relative rotation between theshaft 5 and the end-gear 25 is prevented.

The other portion of the shaft 5, which is not press-inserted into thehole 26, is referred to as an exposed portion 34. The exposed portion 34is provided with a stopper 35 which radially extends. As shown in FIG.3A, the stopper 35 is comprised of a disc portion 37 and astopper-contacting portion 38 which radially outward protrudes from thedisc portion 37.

The accommodation chamber 17 is comprised of a large chamber 40, amiddle chamber 41, and a small chamber 42. The penetrating hole 13communicates with the small chamber 42.

The middle-diameter portion 31 of the end-gear 25 is accommodated in thelarge chamber 40, and the small-diameter portion 32 is accommodated insuch a manner as to extend from the large chamber 40 to the smallchamber 42. The gear portion 28 is accommodated in the actuator case 21.The exposed portion 34 and the stopper 35 are accommodated in the smallchamber 42.

As shown in FIG. 3A, the intake manifold 3 has two stopper walls 44, 45.The stopper-contacting portion 38 comes into contact with one of thestopper walls 44, 45, whereby the rotation of the shaft 5 is regulatedand the operation range of the valve 4 is also regulated.

The stopper wall 44 corresponds to a full-close position of the valve 4and the other stopper wall 45 corresponds to a full-open position of thevalve 4. The small chamber 42 is comprised of a first small chamber 46and a second small chamber 47. The disc portion 37 is accommodated inthe first small chamber 46, and the stopper-contacting portion 38 isaccommodated in the second small chamber 47. The stepped surfacesbetween the first small chamber 46 and the second small chamber 47respectively correspond to the full-close stopper wall 44 and thefull-open stopper wall 45.

When the stopper-contacting portion 38 is brought into a contact withthe full-close stopper wall 44, the valve 4 is positioned at afull-close position. When the stopper-contacting portion 38 is broughtinto a contact with the full-open stopper wall 45, the valve 4 ispositioned at a full-open position. The valve operation range is fromthe full-close position to the full-open position.

Further, since the end-gear 25 rotates along with the shaft 5 and thevalve 4, an operation range of the end-gear 25 is also restricted asshown in FIG. 3B. That is, the operation range of the end-gear 25 isidentical to the valve operation range. When the valve 4 is at thefull-close position, the end-gear 25 is positioned at a full-close gearposition. When the valve 4 is at the full-open position, the end-gear 25is positioned at a full-close gear position.

The gear portion 28 has gear teeth which are able to engage with themiddle gear of the reduction-gears mechanism even if the end-gear 25rotates over the operation range. That is, the gear portion 28 has gearteeth which are comprised of inside gear teeth 49 engaging with themiddle gear in the gear-operation-angle range and outside gear teeth 50engaging with the middle gear in out of the gear-operation-angle range,as shown in FIG. 3B.

In the present embodiment, the gear portion 28 has the gear teeth 49, 50along its entire circumferential periphery. The end-gear 25 can engagewith the middle gear of the reduction-gears mechanism even in out of thegear-operation-angle range.

A concave portion 51 is formed on an end surface of the gear portion 28.The actuator case 21 has a protrusion 52 which is inserted into theconcave portion 51, whereby the end-gear 25 is connected to the actuatorcase 21, as shown in FIG. 2.

The TCV control apparatus is provided with a seal member 53 (forexample, an oil seal or an X-ring) between the engaging portion 27 andthe accommodation chamber 17. An outer surface of the seal member 53 isin contact with an inner surface of the middle chamber 41, and an innersurface of the seal member 53 is in contact with an outer surface of thesmall-diameter portion 32. Thereby, the seal member 53 prevents anair-leakage from the intake passage 2 toward the actuator case 21. Themaximum diameter of the stopper 35 is greater than that of the sealmember 53.

The rotation angle sensor 7 includes a magnet 54 fixed in the end-gear25 and a Hall element 55 detecting magnetic flux generated by the magnet54. Specifically, the magnet 54 is fixed in the end-gear 25 byinsert-molding, and the Hall element 55 is disposed on the actuator case21.

The magnet 54 and the Hall element 55 are arranged in such a manner asto perform a relative movement to each other. When the end-gear 25rotates, a relative position between the magnet 54 and the Hall element55 is varied. The magnetic flux density passing through the Hall element55 is also varied. Based on this variation in magnetic flux density, therotation angle sensor 7 detects the rotation angle of the end-gear 25.Instead of the Hall element 55, a Hall IC or a magnetic resistanceelement can be used.

In the present embodiment, since the rotation angle of the shaft 5holding the valve 4 is identical to the rotation angle of the end-gear25, the opening degree of the valve 4 can be detected by obtaining therotation angle of the end-gear 25.

The ECU has a microcomputer including a central processing unit (CPU), aread only memory (ROM), a random access memory (RAM), an input circuit,an output circuit and a timer.

The ECU functions as a valve position computing means for computing anopening degree of the valve 4 based on the detection value of therotation angle sensor 7.

Also, the ECU functions as a malfunction detecting means for detecting amalfunction in a driving force transmitting path to the shaft 5.

The ECU stores the detection values detected by the rotation anglesensor 7, which correspond to the valve operation range, as normaldetection values. That is, the ECU stores the detection value detectedby the rotation angle sensor 7 in a case that the end-gear 25 rotates inthe gear-operation-angle range.

The malfunction detecting means determines that a malfunction occurswhen the end-gear 25 rotates over the gear-operation-angle range and thedetection value of the rotation angle sensor 7 is out of the normaldetection values. A specific way of detecting a malfunction will bedescribed hereinafter.

[Operation of First Embodiment]

(i) Normal condition

In a case that the end-gear 25 and the shaft 5 are normally connected toeach other, the end-gear 25 rotates from the full-open gear position tothe full-close gear position. Also, the valve 4 rotates from full-openposition to the full-close position. When the stopper-contacting portion38 is brought into contact with the full-close stopper wall 44, thevalve 4 stops rotating at the full-close position. The end-gear 25 alsostops at the full-close gear position.

The rotation angle sensor 7 outputs detection signals which indicate therotation angle of the end-gear 25 is within the gear-operation-anglerange. Thus, the malfunction detecting means determines that nomalfunction occurs.

(ii) Abnormal condition

If the connecting portion between the end-gear 25 and the shaft 5 isbroken, the end-gear 25 rotates over the full-close gear position. Theend-gear 25 rotates free without respect to the full-close stopper wall44. That is, the end-gear 25 rotates out of the gear-operation-anglerange. At this moment, the rotation angle sensor 7 outputs detectionsignals which indicate the rotation angle of the end-gear 25 is out ofthe gear-operation-angle range. Thus, the malfunction detecting meansdetermines that a malfunction occurs in a driving power transmittingpath from the end-gear 25 to the shaft 5. Then, a warning lump is turnedon to notify a passenger of the malfunction.

Besides, in a case that the detection value of the rotation angle sensor7 is proportional to the opening degree of the valve, a lower limitvalue and an upper limit value of the detection value, whichrespectively correspond to the full-close position and the full-openposition, are stored in a memory as a normal detection value of therotation angle sensor 7 corresponding to the valve operation range. Whenthe actual detection value becomes lower than the lower limit value, orwhen the actual detection value becomes higher than the upper limitvalue, it is determined that a malfunction occurs.

[Advantages of First Embodiment]

In the first embodiment, since the valve 4 is connected to the actuator6 by press-inserting the shaft 5 into the end-gear 25, its manufacturingcost can be made lower.

The end-gear 25 can engage with the middle gear of the reduction-gearsmechanism even in out of the gear-operation-angle range. The malfunctiondetecting means determines that a malfunction occurs when the end-gear25 rotates over the gear-operation-angle range and the detection valueof the rotation angle sensor 7 is out of the normal detection valuescorresponding to the valve operation range.

When the driving force is not transmitted from the end-gear 25 to theshaft 5 due to a malfunction, this malfunction can be detected bydetecting the rotation angle of the end-gear 25. Thus, it is unnecessaryto directly detect the rotation angle of the shaft 5 in order to find amalfunction. The manufacturing cost is not increased. A damage of aconnecting portion of the shaft 5 and the end-gear 25 can be detectedwith low cost.

Further, according to the present embodiment, the maximum diameter ofthe stopper 35 is smaller than the diameter of the seal member 53. Thatis, the diameter of the stopper 35 is smaller than the inner diameter ofthe middle chamber 41. Thus, the end-gear 25, the shaft 5, and the sealmember 53 are easily assembled in the accommodation chamber 17.Specifically, after the stopper 35 is arranged in the small chamber 42through the middle chamber 41, the seal member 53 is assembled in themiddle chamber 41. It is less likely that the stopper 35 conflicts withthe seal member 53.

Second Embodiment

Referring to FIGS. 4A and 4B, a second embodiment will be described. Inthe second and the successive embodiments, the same parts and componentsas those in the first embodiment are indicated with the same referencenumerals and the same descriptions will not be reiterated.

The second embodiment is different from the first embodiment in theconfiguration of the stopper. That is, stop-screws 58 are provided onstep-surfaces 57 between the first small chamber 46 and the second smallchamber 47. A tip end of the stop-screw 58 functions as a full-closeposition stopper 44, and a tip end of the other stop-screw 58 functionsas a full-open position stopper 45.

In the second embodiment, the gear portion 28 has gear teeth partiallyalong its circumferential periphery, as shown in FIG. 4B. That is, theinside gear teeth 49 are provided in the gear-operation-angle range, andthe outside gear teeth 50 are provided at both sides of the inside gearteeth 49. The second embodiment has the same advantages as the firstembodiment.

Third Embodiment

Referring to FIG. 5, a third embodiment will be described. The thirdembodiment is different from the first embodiment in the configurationof the stopper and the stopper portion 35. The stopper portion 35 iscomprised of a disc portion 37 and a concave portion 59. Atcircumferential both ends of the concave portion 59, step portions 60are formed.

The inner diameter of the small chamber 42 is slightly larger than theouter diameter of the disc portion 37. A projection 61 is formed on aninner wall surface of the small chamber 42 in such a manner as toproject toward the concave portion 59. One side surface of theprojection 61 functions as the full-open position stopper 45, and theother side surface of the projection 61 functions as the full-closeposition stopper 44. These step portions 60 and stoppers 44, 45 regulatethe operation angle range of the shaft 5. The third embodiment has thesame advantages as the first embodiment.

[Modification]

The rotation angle sensor 7 can be arranged in such a manner as todetect the rotation angle of the actuator 6. That is, the rotation anglesensor 7 may detect the rotation angle of the output shaft of theelectric motor, the motor gear, or the middle gear.

The detection value of the rotation angle sensor 7 may be ON-OFF signal.A switching position between ON-signal and OFF signal is previouslystored. If the detection value is switched at improper switchingposition, it is determined that a malfunction occurs.

The present invention can be applied to a swirl-control-valve controlapparatus, a throttle-valve control apparatus, or an EGR-valve controlapparatus.

Fourth Embodiment

Referring to FIGS. 8A to 10B, a configuration of an electric drivingapparatus will be described.

The electric drive apparatus 301 includes an electric motor 302. Theelectric drive apparatus 301 is applied to a tumble-control-valve (TCV)apparatus 304 which drives a tumble control valve 304.

That is, the TCV apparatus 304 is provided with the tumble control valve303 and the electric motor 302. The tumble control valve 303 isrotatably supported in an intake manifold 306 to adjust the flow passagearea of an intake passage 307.

The valve 303 is fixed on a valve shaft 308. The valve 303 hasrectangular shape. The valve 303 has a notch portion 309.

The drive apparatus 301 is provided with the electric motor 302 and anelectric current detecting means 311 which detects the electric currentsupplied to the electric motor 302. Further, the drive apparatus 301 isprovided with a control means 312 which controls the energization of theelectric motor 302 and a driving circuit 314 which turns on/off theelectric motor 302 according to a control signal from the control means312.

The electric motors 302 is a well-known DC motor which is comprised of arotor 318 having a plurality of coils 316 and a plurality of commutator317, a stator 320 having a plurality of magnets 319, and two brushes 321a, 321 b.

The electric current detecting means 311 is a well-known electriccurrent detecting circuit which detects electric current supplied to theelectric motor 302 based on voltage drop in a shunt resistance 324.

The control means 312 is a microcomputer having a CPU, a ROM, a RAM, aninput device and an output device.

The driving circuit 314 has four switching elements 325 to rotate theelectric motor 302 in the normal direction or the reverse direction.

The rotation torque generated by the electric motor 302 is transmittedto the valve shaft 308 thorough a reduction-gears mechanism. The valveshaft 308 is concentrically connected to an end-gear 326 of thereduction-gears mechanism. An end portion 326 a of the end-gear 326 issupported by the intake manifold 306 through an oil-seal 327.

A stopper 329 is provided to the valve shaft 308.

The stopper 329 is comprised of a disc portion 330 and astopper-contacting portion 331 which radially outward protrudes from thedisc portion 330. The stopper 329 is rotatably accommodated in a chamber332.

The chamber 332 is comprised of a first chamber 333 and a second chamber334. The disc portion 330 is accommodated in the first chamber 333 andthe stopper-contacting portion 331 is accommodated in the second chamber334. Both end walls of the second chamber 334 define stopper walls 335,336.

When the stopper-contacting portion 331 is in contact with the stopperwall 335 or the other stopper wall 336, the valve 303 is mechanicallyheld. When the valve 303 is full-closed, the stopper-contacting potion331 is in contact with the full-close stopper wall 335. When the valve303 is full-opened, the stopper-contacting portion 331 is in contactwith the full-open stopper wall 336.

Thus, even if the valve 303 receives the rotation torque from theelectric motor 302, the valve 303 does not rotate over the full-closestopper wall 335 or the full-open stopper wall 336.

When the stopper-contacting portion 331 is brought into contact with oneof the stopper walls 335, 336 (hold condition), the electric currentsupplied to the electric motor 302 is stepwise increased.

When the valve 303 rotates to the full-open position or the full-closeposition, the electric current supplied to the electric motor 302 variesas shown in FIG. 9B. That is, when the electric motor 302 is energized,the electric current is temporarily rapidly increased due to an inrushcurrent, and then the electric current is decreased. When the valve 303is mechanically held, the electric current supplied to the electricmotor 302 is stepwise increased. The unhold condition is comprised of aninitial condition and a rotation condition. In the initial condition,the electric current supplied to the electric motor 302 is steeplyvaried due to the inrush current. In the rotation condition, theelectric current supplied to the motor 302 is constant and the valve 303rotates in a constant speed. It should be noted that the electriccurrent of the time when the valve 303 is mechanically held is referredto as a lock-current.

The control means 312 stores a threshold “Ithr” with respect to theelectric current supplied to the motor 302. When the electric current istemporarily increased and decreased due to the inrush current, and thenexceeds the threshold “Ithr”, the control means 312 determines that thevalve 303 is normally brought into the hold condition.

That is, after the electric motor 302 is energized, the electric currentexceeds the threshold “Ithr” temporarily due to the inrush current.Then, the electric current is lowered than the threshold “Ithr”. Afterthat, when the electric current excesses the threshold “Ithr” again, itis determined that the valve 303 is normally full-closed or full-opened.

With respect to the temporal increase and decrease in electric currentdue to the inrush current, after the electric current is lowered thanthe threshold “Ithr”, when the absolute value of the temporal variationrate of the electric current is lowered than a specified convergencevalue, the control means 312 determines that a temporal increase anddecrease in electric current due to the inrush current has beenconverged.

Further, the control means 312 functions as a lock-current estimatingmeans which estimates the lock-current. When the valve 303 is in thehold condition, the rotor 318 stops, and each of the brushes 321 a, 321b is in contact with a single commutator 317, the lock-current isdenoted by “Ia”. When at least one of brushes 321 a, 321 b is in contactwith two commutators 317, the lock-current is denoted by “Ib”. Thecontrol means 312 stores a lock-current ratio “Ia/Ib”. The estimatedlock-current is denoted by “Iss”. The threshold “Ithr” is defined insuch a manner as not to exceed an upper value which is obtained bymultiplying “Iss” by “Ia/Ib”.

For example, as shown in FIGS. 10A and 10B, the electric motor 302 hasthree-phase coils 316 a-316 c in delta connection. Each of commutators317A-317C is connected to the coils 316 a-316 c. The resistance value ofthe coils 316 a-316 c is denoted by “r”.

FIG. 10A shows a case in which each of brushes 321 a, 321 b is incontact with only the corresponding commutator 317B, 317C. Thelock-current is denoted by “Ia”. FIG. 10B shows a case in which thebrush 321 a is in contact with the commutators 317A, 317B and the brush321 b is in contact with only the commutator 317C. The lock-current isdenoted by “Ib”.

In a case shown in FIG, 10A, the combined resistance between the brushes321 a, 321 b is expressed by “r×(⅔)”. In a case shown in FIG. 10B, thecombined resistance between the brushes 321 a, 321 b is expressed by“r×(½)”. Thus, the ratio “Ia/Ib” is 0.75 and the threshold “Ithr” isdefined so as to be smaller than an upper value (=Iss×0.75).

In a case that the electric motor 302 has (2N+1)-phase coils 316, theratio “Ia/Ib” can be expressed by (2N+1)/(2 (N+1)). In a case that theelectric motor 302 has 2N-phase coils 316, the ratio “Ia/Ib” can beexpressed by (2N-1)/(2 (N-1)).

After it is determined that the valve 303 is normally brought into thehold condition, the lock-current estimating means defines an average ofa plurality of detection current detected by the electric currentdetecting means 311 as an estimation value “Iss” of the lock-current.

When the valve 303 is rotated to the hold condition next time, thecontrol means 312 defines the threshold “Ithr” smaller than the uppervalue (=Iss×(Ia/Ib)), and determines whether the valve 303 is normallyfull-closed or full-opened.

Further, the control means 312 integrates the electric current from whenthe electric motor 302 is energized until when the electric current isstepwise increased. Based on the integrated value, the control means 312determines whether the rotational position of the valve 303 is normal.That is, in a case that the electric motor 302 is a DC motor, a rotationspeed N(t) [rad/s] of the motor 302 and the electric current I(t) has alinear relation as expressed by following formula (1).

N(t)=a−b·I(t)  (1)

In a case that a time period and a rotation angle of the motor 302 fromwhen the electric motor 302 is energized until when the electric currentis stepwise increased are respectively expressed by T1 [s] and θ [rad],the rotation angle θ can be computed by definite-integrating therotation speed N(t) from 0 to T1 with respect to time “t”. Thus, therotation angle θ can be expressed by following formula (2).

θ=a·T1+·b·∫ ₀ ^(T1) I(t)dt  (2)

As above, since the rotational position of the valve 303 corresponds tothe rotational angle of the electric motor 302, it can be determinedwhether the rotational position of the valve 303 is normal based on theabove integrated value.

[Control Processing of Fourth Embodiment]

Referring to FIGS. 11 to 13, a control processing of the drivingapparatus 301 will be described hereinafter.

FIG. 11 is a main flowchart of a processing in which it is determinedwhether the rotational position of the valve 303 normally reaches thefull-close position in a case that the valve 303 rotates from thefull-open position toward the full-close position. This flowchart startswhen the electric motor 302 is energized.

In step S1, the computer determines whether the valve 303 has moved fromthe initial condition to the rotation condition. When the answer is NO,the procedure proceeds to step S2. When the answer is YES, the procedureproceeds to step S3.

The determination of whether the valve 303 has moved from the initialcondition to the rotation condition is conducted by executing asub-flowchart shown in FIG. 12.

In step S101, the computer determines whether an absolute value “ABVR”of a temporal variation ratio of the electric current is lower than orequal to a specified convergent value “COV”. An absolute value of adifference value between the currently detected electric current and thepreviously detected electric current is defined as the absolute value ofthe temporal variation ratio of the electric current.

When the answer is YES in step S101, the procedure proceeds to stepS102. When the answer is NO in step S101, the procedure proceeds to stepS103. In step S103, the computer determines that the valve 303 has notmoved to the rotation condition. The procedure goes back to step S1 ofthe main flowchart. The answer in step S1 is NO.

In step S102, the computer determines whether the electric current isless than the threshold “Ithr”. When the answer is YES in step S102, theprocedure proceeds to step S104. When the answer is NO in step S102, theprocedure proceeds to step S103. In step S103, the computer determinesthat the valve 303 has not moved to the rotation condition. Theprocedure goes back to step S1 of the main flowchart. The answer in stepS1 is NO.

In step S104, the computer determines that the valve 303 has moved tothe rotation condition. The procedure goes back to step S1 of the mainflowchart. The answer in step S1 is YES.

In step S2, the computer determines whether an elapsed time “Telp1” fromenergization of the motor 302 exceeds an upper limit time of the initialcondition. When the answer is NO in step S2, the procedure goes back tostep S1. When the answer is YES in step S2, the procedure proceeds tostep S4 in which the computer determines that the valve 303 is stuck.The upper limit time of the initial condition is defined based on a timeperiod which is required to converge the temporal increase/closed inelectric current due to the inrush current.

In step S3, the computer determines whether the valve 303 has moved fromthe rotation condition to the hold condition. When the answer is NO, theprocedure proceeds to step S5. When the answer is YES, the procedureproceeds to step S6.

The determination of whether the valve 303 has moved from the rotationcondition to the hold condition is conducted by executing asub-flowchart shown in FIG. 13.

In step S301, the computer determines whether the electric current isgreater than the threshold “Ithr”. When the answer is YES in step S301,the procedure proceeds to step S302. When the answer is NO in step 5301,the procedure proceeds to step S303.

In step S302, the computer determines that the valve 303 has moved tothe hold condition. The procedure goes back to step S3 of the mainflowchart. The answer in step S3 is YES. In step S303, the computerdetermines that the valve 303 has not moved to the hold condition. Theprocedure goes back to step S3 of the main flowchart. The answer in stepS3 is NO.

In step S5, the computer determines whether an elapsed time “Telp2”after the valve 303 has moved to the rotation condition exceeds aspecified upper limit time. When the answer is NO, the procedure goesback to step S3. When the answer is YES, the procedure proceeds to stepS7.

In step S6, the computer determines whether an elapsed time “Telp3”after the valve 303 has moved to the rotation condition exceeds aspecified lower limit time. When the answer is NO in step S6, theprocedure proceeds to step S8 in which the computer determines that amalfunction exists in the rotation position of the valve 303.

The upper limit time and the lower limit time of the rotation conditionare defined based on a time period which is necessary for the valve 303to rotate from the full-open position to the full-close position. Itshould be noted that when the rotation quantity of the valve 303 fromthe full-open position is excessively small, it is determined that amalfunction exists in the rotation position of the valve 303.

In step S7, the computer determines whether the electric current issmaller than a break-wire value. The break-wire value is a referencevalue for determining whether a breaking of wire occurs in the electricmotor 302. When the answer is YES in step S7, the procedure proceeds tostep S9 in which the computer determines that a breaking of wire occurs.When the answer is NO in step S7, the procedure proceeds to step S10 inwhich the computer determines that a disengage malfunction occurs.

The disengage malfunction represents that a disengagement occurs in atorque transmitting path between the electric motor 302 and the valveshaft 308. For example, when a connecting portion between the valveshaft 308 and the end-gear 326 is broken, the end-gear 326 is disengagedfrom the valve shaft 308. Such a breakage is referred to as a disengagemalfunction.

When the answer is NO in step S6, the procedure proceeds to step S11 inwhich the valve 303 is normally rotated form the full-open position tothe full-close position. Then, the procedure proceeds to step S12 inwhich the lock-current is estimated to end the main flowchart.

The control means 312 functions as a lock-current estimating means byexecuting step S12.

[Advantages of Fourth Embodiment]

In a case that the valve 303 rotates from the full-open position to thefull-close position, the control means 312 stores the threshold “Ithr”for determining whether the valve 303 is normally full-closed. After theelectric motor 302 is energized, the electric current exceeds thethreshold “Ithr” temporarily due to the inrush current. Then, theelectric current is lowered than the threshold “Ithr”. After that, whenthe electric current excesses the threshold “Ithr” again, it isdetermined that the valve 303 is normally full-closed.

Thereby, based on the appropriately established threshold “Ithr”, it isable to correctly determine whether the valve 303 is surely moved fromthe rotation condition to the hold condition.

If the valve 303 has not moved from the rotation condition to the holdcondition, the computer determines that the valve 303 is stuck in stepS4, a malfunction exists in the rotation position of the valve 303 instep S8, a breaking of wire occurs in step S9, or the disengagemalfunction occurs in step S10.

Also, after the electric current is lowered than the threshold “Ithr”,when the absolute value of the temporal variation rate of the electriccurrent is lowered than the specified convergence value, the controlmeans 312 determines that the inrush current has been converged and thevalve 303 has moved from the initial condition to the rotationcondition. Thereby, even though the time period required to converge theinrush current fluctuates, the convergence of the inrush current can besurely detected.

The control means 312 stores the ratio “Ia/Ib” and the threshold “Ithr”is defined in such a manner as not to exceed an upper value which isobtained by multiplying “Iss” by “Ia/Ib”. Thereby, without respect to acontact condition between the brushes 321 a, 321 b and the commutators317A-317C, it is surely determined whether the valve 303 has normallymoved from the unhold condition to the hold condition.

Further, the control means 312 integrates the electric current from whenthe electric motor 302 is energized until when the electric current isstepwise increased. Based on the integrated value, the control means 312determines whether the rotational position of the valve 303 is normal.Since the electric current supplied to the electric motor 302 and therotation speed of the motor 302 has a liner correlation, the aboveintegrated value and the rotation angle of the motor 302 has also linercorrelation. The rotation angle of the motor 302 corresponds to therotational position of the valve 303 one-on-one. Therefore, it can bedetermined whether the rotational position of the valve 303 is normalbased on the integrated value with high accuracy.

Fifth Embodiment

As shown in FIG. 14, the driving apparatus 301 is provided with atemperature estimating means 340 which estimates ambient temperaturearound the electric motor 302, and a voltage detecting means 341 whichdetects voltage of electric power source 313. The electric motor 302receives electricity from the electric power source 313. The voltagedetecting means 341 is a well-known voltage detecting circuit whichoutputs detection signal to the control means 312. The temperatureestimating means 340 is a water-temperature sensor which detects enginecoolant temperature. The ambient temperature around the motor 302 isestimated based on the engine coolant temperature.

Also, the control means 312 stores a ratio between the lock-current andthe power source voltage as a function P(T) of the ambient temperatureT. This ratio is referred to as hold-condition conductance. Morespecifically, as shown in FIG. 15A, the control means 312 stores theambient temperature and the hold-condition conductance as a table dataof “T” and “P(T)”.

The control means 312 applies the estimation value of the ambienttemperature to the function P(T) to compute the hold-conditionconductance. The control means 312 computes an estimation value “Iss” ofthe lock-current by multiplying the hold-condition conductance and thedetection value of the power source voltage.

The threshold “Ithr” is defined in such a manner as not to exceed anupper value which is obtained by multiplying “Iss” and “Ia/Ib”.

Furthermore, the control means 312 corrects the function P(T) based onthe detected electric current, the estimated ambient temperature aroundthe motor 302, and the detected power source voltage. Specifically, thedetected value of the lock-current is divided by the detected value ofthe power source voltage so that the actual measured value “P” of thehold-condition conductance is computed. Based on the actual measuredvalue “P”, the table data of the function P(T) is updated.

For example, in a case that the estimated value of the ambienttemperature around the motor 302 is Ts° C. (0° C.<Ts<20° C.), a ratiobetween a difference (Ts−0) and a difference (20−Ts) is defined as“s:(1−s)” (0<s<1), the hold-condition conductance obtained based onnot-updated P(0) and P(20) is denoted by P(Ts), and the differencebetween “P” and “P(Ts)” is denoted by “ΔP(Ts)”.

In this case, after a weighting is performed with respect to not-updatedP(0) and P(20) according to Ts° C., the updated P(0) and P(20) areexpressed as follows:

Updated P(0)=not-updated P(0)+k·(1−s)·ΔP(Ts)

Updated P(20)=not-updated P(20)+k·s·ΔP(Ts)

wherein k=1/(2s ²−2s+1).

[Advantages of Fifth Embodiment]

According to the fifth embodiment, the driving apparatus 301 is providedwith a temperature estimating means 340 which estimates the ambienttemperature around the electric motor 302, a voltage detecting means 341which detects the power source voltage. The control means 312 computesthe hold-condition conductance based on the table data which shows arelation between the ambient temperature around the motor 302 and thehold-condition conductance. Further, the estimation value “Iss” of thelock-current is computed by multiplying the hold-condition conductanceand the detection value of the power source voltage. Thereby, theestimation value “Iss” of the lock-current can be computed in view ofthe thermal characteristic.

Further, the control means 312 corrects the table data based on thedetected value of the electric current supplied to the motor 302, theestimation value of the ambient temperature around the motor 302 and thedetection value of the power source voltage. Thereby, even if thecharacteristics of the electric motor 302 are varied with age, thehold-condition conductance in the table data can be updated with highaccuracy. Even if the characteristics of the electric motor 302 arevaried with age, the lock-current can be estimated with high accuracy.

Sixth Embodiment

According to a sixth embodiment, as shown in FIGS. 16A and 16B, thecontrol means 312 outputs PWM-signals to four switching elements 325 ofa driving circuit 314 so that the energization of the motor 302 iscontrolled. A sampling frequency at which the control means 312 obtainsthe detection values from the current detecting means 311 is greaterthan a value which is obtained by dividing the frequency of thePWM-signals by a duty ratio of the PWM-signals. Thereby, since thedetection value of the electric current is surely obtained duringON-period of the PWM-signals, it can be avoided that the detection valueof the electric current is obtained only during OFF-period of thePWM-signals.

The control means 312 does not use detection value which is lower than areference value, when executing processings shown in FIGS. 4-6. Thus,erroneous determinations can be avoided.

[Modification]

The driving apparatus 301 is not limited to the above embodiments. Forexample, it can be determined whether the rotational position of thevalve 303 normally reaches the full-open position in a case that thevalve 303 rotates from the full-close position toward the full-openposition.

The hold condition can be generated at a middle position between thefuel-open position and the full-close position. The driving apparatuscan be applied to a throttle valve control apparatus or an EGR gascontrol apparatus.

In the above embodiments, the valve 303 is a butterfly valve.Alternatively, the valve 303 may be a poppet valve or a needle valve.

In a case that the valve 303 is a poppet valve, the driving apparatus301 controls a linear movement of the poppet valve.

1. A valve control apparatus comprising: a valve opening/closing a fluidpassage; a shaft supporting the valve; a housing accommodating the valveand the shaft therein; an actuator having a reduction-gears mechanismwhich transmits a decelerated rotational force of a motor to the shaft;a sensor detecting a rotation angle of the actuator; and a malfunctiondetecting means for detecting a malfunction in arotational-force-transmitting path to the shaft, wherein thereduction-gears mechanism includes an end-gear engaging with a gear ofthe motor to transmit the rotational force of the motor to the shaft,the end-gear is provided with a connecting portion and gear teethengaging with the gear of the motor, the connecting portion is made ofresin material and is provided with a press-insert hole, the shaft has apress-insert portion which is press-inserted into the press-insert hole,an exposed portion which is out of the press-insert hole, and a stopperwhich radially extends from the exposed portion, the housing has astopper surface with which the stopper is brought into contact, so thata valve operation range is regulated, the gear teeth is comprised ofinside gear teeth and outside gear teeth, the inside gear teeth engageswith the gear of the motor in a gear-operation-angle range of theend-gear which corresponds to the valve operation range, the outsidegear teeth engages with the gear of the motor in out of thegear-operation-angle range, and the malfunction detecting meansdetermines that a malfunction occurs when the end-gear rotates over thegear-operation-angle range and the detection value of the rotation anglesensor is out of normal detection values which correspond to the valveoperation range.
 2. A valve control apparatus according to claim 1,wherein the end-gear has the gear teeth along an entire circumferentialperiphery.
 3. A valve control apparatus according to claim 1, whereinthe end-gear has the gear teeth partially along a circumferentialperiphery.
 4. A valve control apparatus according to claim 1, whereinthe sensor includes a magnet fixed to the end-gear and an elementdetecting magnetic flux generated by the magnet.
 5. A valve controlapparatus according to claim 1, wherein the fluid passage is an intakepassage communicating with a combustion chamber of an internalcombustion engine.
 6. A valve control apparatus according to claim 1,wherein the fluid passage is an intake passage communicating with acombustion chamber of an internal combustion engine, the housing definesthe intake passage and an accommodation chamber which accommodates theend-gear.
 7. A valve control apparatus according to claim 6, furthercomprising a seal member which air-tightly seals between the connectingportion and an inner wall of the accommodation chamber.
 8. A valvecontrol apparatus according to claim 7, wherein a maximum diameter ofthe stopper is smaller than an outer diameter of the seal member.
 9. Anelectric driving apparatus comprising: an electric motor generating adriving force while receiving an electric current; an electric currentdetecting means for detecting the electric current supplied to theelectric motor, and a control means for controlling an energization tothe electric motor so that the driving force is transmitted to a drivenmember in order to vary a displacement magnitude which represents atleast one of a variation in position of the driven member and avariation in posture of the driven member, wherein the displacementmagnitude includes a hold value at which the driven member ismechanically held and the displacement magnitude does not vary eventhough the driving force is continued to be transmitted from theelectric motor to the driven member so as to vary the displacementmagnitude in one direction, the electric current supplied to theelectric motor is stepwise increased when the displacement magnitudereaches the hold value after the displacement magnitude has been variedin one direction, the control means stores a threshold regarding theelectric current supplied to the electric motor for determining whetherthe displacement magnitude normally reaches the hold value in a casethat the electric motor is controlled in such a manner that thedisplacement magnitude reaches the hold value after the displacementmagnitude has been varied in one direction, and after the electric motoris energized, the electric current exceeds the threshold temporarily dueto the inrush current, then the electric current is lowered than thethreshold, and when the electric current excesses the threshold again,the control means determines that the displacement magnitude hasnormally reached the hold value.
 10. An electric driving apparatusaccording to claim 9, wherein after the electric current is lowered thanthe threshold, when an absolute value of a temporal variation rate ofthe electric current is lowered than a specified convergence value, thecontrol means determines that a temporal increase and decrease inelectric current due to the inrush current has been converged.
 11. Anelectric driving apparatus according to claim 9, wherein the electricmotor includes a rotor having a plurality of coils and a plurality ofcommutators, a stator having a plurality of magnets, and two brushesbeing in contact with the commutators to supply the electric current tothe coils, the electric motor generates a rotational torque, the controlmeans includes a lock-current estimating means for estimating alock-current which is supplied to the electric motor after thedisplacement magnitude has reached the hold value, when the displacementmagnitude reaches the hold value, the rotor stops and each of thebrushes is in contact with the single commutator, the lock-current isdenoted by “Ia”, when at least one of brushes is in contact with themultiple commutators, the lock-current is denoted by “Ib”, the controlmeans stores a lock-current ratio “Ia/Ib”, and the threshold is definedin such a manner as not to exceed an upper value which is obtained bymultiplying the estimated lock-current and the lock-current ratio“Ia/Ib”.
 12. An electric driving apparatus according to claim 11,wherein the lock-current estimating means defines an average value of aplurality of electric current values detected by the electric currentdetecting means as the estimation value of the lock-current after it isdetermined that the displacement magnitude normally reaches the holdvalue.
 13. An electric driving apparatus according to claim 11, furthercomprising: a temperature estimating means for estimating an ambienttemperature around the electric motor; a power source voltage detectingmeans for detecting a voltage of a power source which supplies anelectricity to the electric motor, wherein the lock-current estimatingmeans stores a ratio between the lock-current and the power sourcevoltage as a function of the ambient temperature around the electricmotor, the lock-current estimating means computes said ratio between thelock-current and the power source voltage by applying the estimatedvalue of the ambient temperature to the function, and the lock-currentestimating means computes an estimation value of the lock-current bymultiplying said ratio and the power source voltage.
 14. An electricdriving apparatus according to claim 13, wherein after it is determinedthat the displacement magnitude normally reaches the hold value, thelock-current estimating means corrects the function based on a detectionvalue of the electric current detected by the electric current detectingmeans, an estimate value of the ambient temperature around the electricmotor estimated by the temperature estimating means, and a detectionvalue of the power source voltage detected by the power source voltagedetecting means.
 15. An electric driving apparatus according to claim 9,wherein the control means integrates the electric current supplied tothe electric motor from when the electric motor is energized until whenthe electric current is stepwise increased, and the control meansdetermines whether the displacement value is normal based on theintegrated value.
 16. An electric driving apparatus according to claim9, further comprising a driving circuit which turns on/off the electricmotor according to a control signal from the control means, wherein thecontrol means outputs a PWM-signal as the control signal to the drivingcircuit to control an energization of the electric motor, and a samplingfrequency at which the control means obtains the detection values fromthe current detecting means is greater than a value which is obtained bydividing the frequency of the PWM-signal by a duty ratio of thePWM-signal.